diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index d2b2b1b62a..c4fa065c01 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -2401,7 +2401,7 @@ class Cache:
 
         Example: Assume author A has link X, author B has link Y, tag S has link
         F, and tag T has link G. If book 1 has author A and tag T,
-        this method returns {'authors':{'A':'X'}, 'tags':{'T', 'G'}}
+        this method returns {'authors':{'A':'X'}, 'tags':{'T', 'G'}}.
         If book 2's author is neither A nor B and has no tags, this method returns {}.
 
         :param book_id: the book id in question.